tests/heapalloc, heapalloc_super: Skip in strict stackless mode.

These tests involves testing allocation-free function calling, and in strict
stackless mode, it's not possible to make a function call with heap locked
(because function activation record aka frame is allocated on the heap).

tests/micropython/heapalloc.py

@@ -2,6 +2,15 @@
 
 import micropython
 
+# Check for stackless build, which can't call functions without
+# allocating a frame on heap.
+try:
+    def stackless(): pass
+    micropython.heap_lock(); stackless(); micropython.heap_unlock()
+except RuntimeError:
+    print("SKIP")
+    raise SystemExit
+
 def f1(a):
     print(a)
 

tests/micropython/heapalloc_super.py

@@ -1,6 +1,15 @@
 # test super() operations which don't require allocation
 import micropython
 
+# Check for stackless build, which can't call functions without
+# allocating a frame on heap.
+try:
+    def stackless(): pass
+    micropython.heap_lock(); stackless(); micropython.heap_unlock()
+except RuntimeError:
+    print("SKIP")
+    raise SystemExit
+
 class A:
     def foo(self):
         print('A foo')